The storage capacity of a storage apparatus that makes use of storage media, such as a magnetic disk, a magneto-optical disk, and an optical disk, is being increased. As to an increase in storage capacity of a storage apparatus, a technique to configure a storage apparatus that has improved reliability by integrating a plurality of storage media called RAID (Redundant Arrays of Inexpensive Disks) is widely known.
Further, a storage apparatus that uses the RAID is also used, in which a nonvolatile semiconductor memory, such as a SSD (Solid State Drive) using a flash memory, excellent in random access performance is used as a storage medium to improve data access at the time of random access.
However, there is a limit to the number of write operations of a semiconductor memory, such as a flash memory, when in use, and it is not possible to perform writing a predetermined number of times or more. As described above, there is a storage medium in which an upper limit is set to the number of write operations in terms of the number of times of use, the in-use time, etc.
For the management of the number of write operations of a semiconductor memory, there are some known techniques. Please see, for example, Japanese Laid-Open Patent Publications Nos. 2010-146220, 2004-118407, and 08-96589.
Here, the storage apparatus uses a RAID including a plurality of storage media, but, there is such a problem that it becomes necessary to perform replacement when a plurality of storage media reaches an upper limit of the number of write operations at the same time or that there is a case where redundancy is not maintained when a failure occurs.